


Thirteen Weeks

by Everyday_Im_Preaching



Category: Gravity Falls
Genre: Alpha/Beta/Omega Dynamics, Alpha/Omega, Car Sex, Cute, Fluff, M/M, Plot What Plot/Porn Without Plot
Language: English
Status: Completed
Published: 2016-12-06
Updated: 2016-12-06
Packaged: 2018-09-06 20:22:01
Rating: Mature
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 1,877
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/8767909
Author URL: https://archiveofourown.org/users/Everyday_Im_Preaching/pseuds/Everyday_Im_Preaching
Summary: Bill is far too impatient; he doesn't see the point of waiting until they get home when he has a perfectly good back seat.





	

**Author's Note:**

  * For [SmartyDragon](https://archiveofourown.org/users/SmartyDragon/gifts).
  * Inspired by [Nowhere To Go But Down](https://archiveofourown.org/works/6403753) by [Everyday_Im_Preaching](https://archiveofourown.org/users/Everyday_Im_Preaching/pseuds/Everyday_Im_Preaching). 



> This is not a canon part of the NTGBD universe.
> 
> This fic is gifted to SmartyDragon--you've been working so hard, take some time to relax!

"You're kidding. You can't actually think this is going to work," Dipper told the alpha dryly through panting breaths; his upper torso was jammed against the car door, the handle digging into his back. Bill didn't seem to care about whether it waspossible, he just cared about getting it done. That's why they were laying there, after all.

" _Plenty_ of people have car sex," Bill countered, hands greedily pawing at Dipper's belt. Dipper twisted his hips in assistance, trying to give the slender fingers more room to work.

"Yeah, but plenty of people aren't six feet tall," Dipper said dryly, cocking an eyebrow. Bill let out a playful rumble; unhooking the belt and with a tug, pulled it free. "What if someone finds us?"

"Then they'll have quite the show to enjoy, won't they?" Bill asked. He frowned at the way Dipper was pressed up against the door. Sitting up, he reached for something underneath the front seat. "Lean up." It was hard to see what he'd been grabbing at in the dark.

"What are you planning?" Dipper questioned, pulling himself into a seated position. Bill was taking out a thick, worn set of quilts from underneath the passenger seat. Dipper squinted, recognising them from the picnic that they'd gone on the week before. The alpha slipped them behind the omega, padding the door and forcing him to sit up more.

"Comfy?" he asked, tugging Dipper's pants and boxers down just enough to reveal his erection. Bill licked his lips at the sight of it. "Mm, looks like someone's just as excited as I am," he breathed; Dipper's breath hitched as a hand circled his cock. "You're always hungry for me, aren't you?" Dipper bucked his hips up.

"Yes, fucking _yes_ ," Dipper whined, trying to widen his legs. His jeans held them in place, keeping them pinned at a frustrating angle that wasn't wide enough,in the omega's opinion. Bill didn't seem in the mood to help, though - he was too busy undoing his own belt single-handedly as he fisted Dipper's cock. "Bill." The alpha's eye snapped up to look at his omega, tongue darting out to lick his lips.

"Oh, my little tree," he rumbled; his hand temporarily left his belt so it could plant itself beside Dipper. He moved up between the pinned legs, kissing the omega and pouring every bit of lust into it. Darting his tongue into the pliant mouth, Bill plundered it with a number of groans and growls, inhaling the arousal of his mate as he tugged at his cock.

"No, no..." Dipper hissed when he was let up for air. "Pants… Pants off," he whined, trying to shove his knees apart, and thrashing his head back and forth against the quilt. Bill tilted his head down and chuckled lightly, helping tug jeans and undergarments the rest of the way off.

"You poor thing. So wet and ready for me. All you want is me between these beautiful thighs of yours, and I was impeding you," Bill told him with a warm, cheerful rumble. He squeezed one of Dipper's thighs playfully.

"Not beautiful," Dipper croaked out... How could the inside of the vehicle be so hot when it had been freezing outside?

"Not beautiful? I have to disagree." Bill was nipping along Dipper’s jaw now. "I have dreams about these thighs, locked around my head as I suck you off. Wrapped tightly around my waist as I piston and rock into you, grounding yourself against me."

" _Fuck_ ," Dipper hissed; Bill had nipped a bit harder, drawing blood. A wet tongue darted out to lick up the tiny crimson beads, catching them before they had a chance to roll away. "Could you not do that?"

"But _why_?" Bill whined loudly in his ear; Dipper could hear Bill's belt jangling as he continued to undo it. Dipper's legs were pushed apart farther, one foot scraping along the back seat while the other searched for purchase and found none; it slid along the back of the passenger seat and onto the carpeted floor with a jolt.

"Because it _hurts_ ," Dipper whined back mockingly. Bill smiled, kissing the bite. "Can't you just mark me with hickies like a normal person?" The alpha trilled lightly at the suggestion.

"Oh, you like being marked?" Bill teased - Dipper bucked his hips up as the hand around his cock left, going to grip his hip instead. He let out a displeased whine. "I wonder. Is that an omega thing, or is that something my sugar pine likes?"

"Could be both," Dipper replied, wiggling his hips in need. Bill's free hand had dipped between his cheeks, gathering some of the slick there and bringing it up his mouth. "Oh, gross." The omega turned his head away, pretending to wretch as Bill licked it from his fingers.

"You might be grossed out, but I find the taste of you divine. If you weren't so insistent that I keep my mouth occupied with other areas, I would lick you open every day." Bill smirked. The alpha hadn't bothered to completely remove his pants; instead he slipped his hand in and tugged his cock out, palming and stroking it.

"My ass isn't something for you to lick," Dipper told him obstinately.

"Says you," the alpha crooned. "I'll have you know it's quite common for alpha's to lick their omegas clean after lovemaking."

"If you don't stop talking about it, I swear to god I'm going to put my pants back-" Dipper began; he cut himself offwith a sharp intake of breath as BIll pushed inside, all of his teeth showing in a happy, hungry grin. " _F-Fuck you,_ " the omega hissed in a stutter while the older man pet his thighs, eye twinkling in mischief.

"But isn't this so much better?" Bill hummed, both hands slipping underneath Dipper's legs and tugging them up and over the alpha's shoulder's. Doubling over the smaller man, he forced the omega's body to fold down onto itself. With a languid rock of his hips, he pulled out and shoved back into the man beneath him, angling himself so that he could thrust deep and hard. Dipper let out a soft groan, despite the discomfort that came from how his body was contorted.

"Yes," Dipper breathed. Bill let out a quiet snicker.

"How hard can I fuck you?" the alpha asked suddenly. His hips had stilled, forcing the omega to focus. Dipper blinked at him for a moment, trying to make sense of the question. His mind was already getting hazy. "I really, really want to fuck you until you can't walk." At the suggestion, Dipper's hips twitched up and an excited trill left him. "Use your words, sugar pine."

"Hard. Please. Fuck me hard,"Dipper whined, rolling his hips against his alpha. Bill's eye flashed with excitement. With a rumbling growl, he pulled all the way out before slamming back into Dipper, forcing him against the quilt with all of his weight. A strangled cry left Dipper and his hands flew back to brace himself against the door.

Bill's claws dug into Dipper's thighs as he bent himself even further over the younger man, ramming into him with an impatient, erratic pattern. The unpredictable thrusts left Dipper disoriented as he tried to push his hips up to meet them. Dipper's fingers were white-knuckled as they gripped the cloth covered plastic beneath them. He was letting out an endless, breathless stream of keens and groans as Bill panted above him.

"Do you like this?" Bill huffed out, not sounding nearly as smooth and dominant as usual. It was almost worth a laugh, how hard the alpha was trying to keep his cool. When Dipper let out a warble and bucked his hips in answer, Bill laughed. "You do."

"Love you in any way I can have you," Dipper managed to choke out, greedily sucking in air between words. A particularly rough thrust against his prostate had him arching his back up towards Bill; a slender fingered hand slipped down to splay across his stomach, reverently petting the slightly pudgy flesh.

"Soft and squishy," he took a moment to tease, cradling it in his clawed fingers. Dipper swatted at him weakly.

"S-stop that. It's your fault I'm getting fat," he breathed in a low whine.

"Healthy. You're _healthy_. Not fat." Bill's tone was suddenly serious; he was slamming the head of his cock against Dipper's prostate with every thrust now, pulling out until just the head remained in Dipper before sinking back in. The omega's voice rose again in pleasure, nearly howling with it. "You're so gorgeous. In every way, I just can't get over you," Bill hissed.

"Bill, I--" Dipper began, but his orgasm crashed over him then in a heavy wave.Dipper’s body seized up, tightening around the alpha's cock and drawing a broken cry as his cum splattered on his stomach. Bill let out a possessive snarl, nails drawing thin red lines on pale flesh as he drove his own release deep into the omega beneath him.

Dipper loved to see the alpha come undone, and today - today was no different. The alpha's back arched slightly upward, lips drawn back from his teeth in a snarl. Through the diluted, pale light filtering through the window, the omega took a moment to really admire the older man. Muscles tight and coiled as his hips stilled, eye slightly glazed in pleasure; his fingers would loosen, then tighten, then trace soft circles into bruised flesh as he came down from his high.

 

Dipper pressed his still heated cheek to the cool of the window, lazily puffing out warm breaths of air and watching the window fog over and slowly clear. Bill was humming along to the song on the radio, tapping his hands on the wheel.

"'S'not what I was talking about," Dipper suddenly murmured.

"Hm?" Bill slid a hand across the console to lay it on Dipper's thigh. "What's wrong, sugar pine?" He rubbed at the skin there, as if trying to soothe the omega.

"That wasn’t what I meant when I said it was your fault I was getting fat. Was going to tell you as soon as we left, but you got handsy." He struggled to sit up, mouth opening into a soft yawn. Bill frowned.

 "What do you mean, then?" Bill questioned.

"I'm pregnant. Thirteen weeks," Dipper told him, sliding a hand over Bill's. The alpha's silence was deafening, seconds ticking by like hours.

"Pregnant? You mean...the trial, it-" It was like Bill had forgotten how to work his vocal cords. "Dipper, you're..." He struggled for a moment, hands squeaking against the leather of the steering wheel. "We're... You're. _You're_ pregnant. We're going to have to raise a tiny person! Oh lord, what are we going to name it?" His face was growing into one of glowing excitement. Dipper let out a sleepy laugh, settling back against the window. Fat snowflakes had begun to spiral down from the sky, sticking to the ground and dusting the trees that they passed.

"I'm excited to see the great Cipher method of parenting," Dipper remarked, entwining his fingers with Bill's. Bill let out a soft chuckle.

"I love you," the alpha whispered. "I love you so _much_."

**Author's Note:**

> Hey!
> 
> Song for this fic:  
> Tiny Face (As You Are) by Will Currie
> 
> Want to stay updated? Click [here](http://everyday-im-preaching.tumblr.com/) to stay in the know!


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